In convenience stores spawned by the wellness wave, kombucha slushies take the place of corn-syrupy treats infused with red dye, tortilla chips are made of cassava flour instead of corn and there are vegan ice cream bars and a dizzying selection of organic produce and craft beer on tap.

Traditional corner markets have been notching up their healthier options in recent years, selling pre-made salads, nut milks and organic yogurts.

But a new crop of niche stores aimed at millennials who can afford to pay more have completely overhauled the shelves, making gluten-free and organic products their staples, not just the side dish, along with compostable straws and on-demand delivery. These shoppers also like to see their stores support what they consider worthy causes.

"We think of our stores as a human recharging station as opposed to the traditional convenience store, which tears down your health," said Lisa Sedlar, who's about to open her fourth Green Zebra Grocery in Portland, Oregon.

The store sells so much kombucha that it recently launched its own line of kombucha slushies with flavors including pineapple ginger and marionberry mint. It also offers itself as a pickup spot for customers who have pre-ordered weekly boxes of fresh produce from local farms.

There's even a store on Portland State University campus to satisfy late-night dorm cravings. That store attracts about 1,500 visits a day with coconut sugar and gluten-free flour in bulk bins, and other health-oriented goods.

Analysts say millennials, who are willing to pay a premium for higher-quality ingredients and want to support companies in line with their values, are a driving force behind the trend for stores that are popping up around the country from Los Angeles to Philadelphia.

A 2018 report from EuroMonitor says convenience stores are changing their image to appeal to a more health-conscious generation, stocking up on gluten-free, grass-fed and organic products.

While "portability and grab-and-go convenience remain critical, millennial dietary habits stand to revolutionize a channel that has been anything but health-conscious in the past," the report says.

At least 200 stores fall into this category in the United States, said Jeff Lenard, a vice president with Advancing Convenience & Fuel Retailing. And while that's still a small segment of the 154,000 convenience stores in the U.S., he said it's likely to grow.

Everything at The Goods Mart in Silver Lake, California, is free of artificial flavors and dyes, nitrates and genetically modified ingredients. Customers choose from healthy snacks, $4 breakfast burritos and ugly fruit provided through a partnership with a local farmer, including avocados that cost only 50 cents.

There are no single-serve plastic bottles or plastic straws. Instead the coffee and slushies come in recycled paper cups with compostable paper straws, although many customers buy metal or glass straws at the cash register.

Customers can also donate up to 5 percent of their bill to charity, including a local homeless mission, says founder Rachel Krupa.

"I don't believe it's a passing fad," said David Portalatin, food industry adviser for trend group NPD. "People bring the same demand for convenience but with a whole new set of food values to go along with it."

Choice Market in Denver even created its own delivery app for consumers who want their gourmet sandwich, organic produce and craft beer on demand. About 30 percent of the store's sales are delivery.

"It's such a big piece of our target market and how they shop," said CEO Mike Fogarty, who donates leftovers to a local food bank.

The response has been so strong that construction has started on two additional stores, including one in partnership with the Denver Housing Authority to service low-income neighborhoods lacking nearby grocery stores with healthier foods and fresh produce and to hire at-risk youth.

The checkout counter at Mendez Fuel in Miami is filled with the expected cigarettes, lottery tickets and mini bottles of whiskey, but there's also a large selection of high-end dark chocolate. Behind the cafe counter sits a massive prep bowl of leafy greens next to a woman pouring filling into handmade vegan empanadas.

A large line has formed waiting for orders off a menu that includes smoothies with algae, bee pollen, matcha and other superfoods. They also serve house-made, organic, cold-pressed juices and have a vast selection of craft beer.

Jay Mayorga, a 25-year-old barber who works nearby and follows a paleo diet, stops in about four times a week for a green smoothie or acai bowl and he usually grabs some jerky or a protein bar.

"Paleo is hard to find so I like that," he said.

The store has a large selection of vegan, paleo, keto and other healthy snacks including specialty nut butters, non-dairy cheeze puffs and grain-free tortilla chips.